Inter-phase Voltage Balance Control of Cascaded H-bridge STATCOM Based on Disturbance Observer
In view of imbalance of inter-phase capacitive voltage due to grid voltage drop and imbalance of cascaded H-bridge STATCOM under complicated conditions,a feedforward control based on disturbance observer is proposed.The power distribution of the cascaded H-bridge STATCOM is studied,and the reason of inter-phase unbalance of the cascaded H-bridge STATCOM is analyzed.The negative sequence power is regarded as disturbance for negative sequence power feedforward.Considering the model difference and the influence of deviation caused by various disturbances and also according to the active power exchange between AC side and DC side,the DC power is feedforward to the output end of inter-phase voltage balance control after DOB observation,and the inter-phase voltage balance control of the cascaded H-bridge STATCOM is achieved by zero sequence power injection.Finally,a cascaded H-bridge STATCOM simulation model is set up in MATLAB/Simulink.The simulation results verify that the control strategy can improve the rapidity,follow ability and robustness of the inter-phase voltage balance of the system under complicated conditions.
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